You probably know this already but i'm going to post it in case you don't. It may give you some things to look at for the source of the problem.
CODE 44
Trouble Code 44 indicates that the O2 sensor is showing a persistently
high exhaust oxygen content (lean), despite the efforts of the ECM to increase injector on-time (thus increasing fuel delivered). Integrator and
BLMnumbers may indicate > 128 by a substantial margin.
The conditions for setting this code are:
- no Code 33 or Code 34 (MAF Error) present, and
- the O2 sensor voltage remains below 250 mVolts, and
- the ECM is in Closed Loop control, and
- the above conditions exist for more than 50 seconds.
Typical causes for this code include:
1) O2 sensor defective or lead shorted
2) Lean injectors (dirty or blocked)
3) Water in fuel
4) Exhaust leaks upstream of O2 sensor
5) Fuel pressure or volume too low
6) MAF sensor reading lower airflow than is actually present
7) Vacuum leaks
8) Incorrect or poorly calibrated PROM